The hydrophobic biological, synthetic, and natural petroleum component substances which are transferred within marine food chains are being studied in an effort to understand the basic processes regulating their transfer and detoxication in marine organisms. The naturally occurring hydrocarbons, in particular, will be studied in their passage from alga to crustacean to vertebrate. The site and mode of storage of these materials should reveal related processes for toxic hydrocarbon transfer and storage. The metabolic reactions which produce hydrocarbons in marine organisms and those by which they are metabolized are under investigation. It is anticipated that the unique chain lengths of these hydrocarbons will provide an effective means of tracing their presence in the food chain. The relative toxicities of certain aryl hydrocarbons varies in related marine species. Study of metabolism of these substances on a comparative basis may allow establishment of criteria for pollutant levels in marine environments.